1. Field of the Invention
This invention relates to an electric part holding device in which an electric part such as an IC or a carrier for carrying thereon an electric part is held by semi-elliptic springs mounted on a base, the curvatures of which are reversible between an inwardly convex and an inwardly concave curvature.
2. Brief Description of the Prior Art
In Japanese Utility Model Publication No. Sho. 58-46545, the electric part is accommodated within the electric part accommodation portion formed in the base, and the electric part is held within the accommodation portion by the semi-elliptic springs which can be moved inwardly and outwardly between inwardly concave and inwardly convex curvature, the springs being disposed along two opposite sides (on a defining wall forming the two sides) of the electric part accommodation portion, the springs being engaged with the two sides of the electric part for holding the electric part when the springs are inwardly convex.
Each of the semi-elliptic springs is provided at both ends thereof with shaft holes, and the shaft holes are engaged with threaded shafts, etc. projecting from both ends of each side of the accommodation portion in order to form the semi-elliptic shape for storing spring force.
However, the above conventional device has the following problems. Since the semi-elliptic springs are disposed along the two opposite sides of the accommodation portion and engaged with the two opposite sides of the electric part when the springs are in the inwardly convex positions, when this technique is applied to an IC carrier and the IC carrier is placed on the socket, the semi-elliptic springs disposed along the two sides of the IC carrier (base) interfere with the IC leads and the contacts of the socket when the semi-elliptic springs are brought to the inwardly convex curvature, and as a result, the springs and the carrier can not be contacted with each other.
In the case where the semi-elliptic springs disposed along the two opposite sides of the base are engaged with the two sides of the electric part as in the prior art, springs of a long stroke are required so that they can engage with the electric part along generally the entire length of the two sides, in order to hold the electric part surely and stably. In addition, the springs occupy a large space above the electric part, and this is a bar to installing a cooling device, etc.
Furthermore, when the semi-elliptic springs are inwardly convex from the two sides of the base, the amount of engagement (engaging depth) with respect to the electric part is naturally limited (the engaging depth is shallow). If the amount of movement upon reversal of curvature, i.e., the curvature of each semi-elliptic spring, is set to be large in order to obtain a sufficient amount of engagement with the electric part, the curved portion is caused to extend out of the base when the spring is outwardly convexly curved. As a result, the device becomes large in size and the springs are likely to be deformed.
In the prior art, since the curvatures of the springs are reversed in parallel with the upper surface of the electric part and engaged with the upper surface, it is difficult to obtain an intimate contact between the springs and the upper surface of the electric part. At least, it is impossible to apply a pressing force thereon by the springs. In addition, play occurs between the springs and the electric part due to manufacturing and assembling variations, etc. As a result, a harmful loosening of the electric part in the holding device may occur.
Moreover, in the prior art, since the both ends of the springs are mounted on the base on the shafts, much time and labor is required for assembling. In addition, it takes such additional labor because the shaft inserting portions are wound at both ends of the springs and female screw holes are formed in order to mount the shafts therein. Therefore, the number of parts are increased.